In many energy storage technologies, because of a light weight, a small volume, a high working voltage, high energy density, high output power, high charging efficiency, no memory effect, a long cycle life and other advantages, lithium ion batteries are widely applied to mobile phones, notebook computers, and other fields. In recent years, with the increase of application requirements for small-size portable devices, high-power electric automobiles, and the like, the idea of developing a lithium ion battery with higher energy density and higher power density becomes more urgent.
At present, an existing problem is as follows: an electrolyte and a cathode material react on a solid-liquid interphase layer to form a SEI film in a first-time cyclic process of a lithium ion battery system, and this process consumes lithium in active substance of the cathode material, which results in reduction of initial capacity of the lithium ion battery. Generally, the cathode material loses 10 percent capacity in a first-time charge-discharge process, and if a silicon material (4200 mAh/g and 9786 mAh/cm3) with higher specific capacity is used, a first-time coulombic efficiency is even lower than 85 percent, directly resulting in loss of a plenty of capacity. In addition, the specific surface area of the cathode material is larger when the first time efficiency is lower.
For this, a current solution includes: (1) form a SEI film in priority before assembling a lithium ion battery, so as to reduce loss of inreversible capacity, for example, in the patent application document with the publication number CN102148401A, Shenzhen CBAK company indicates that a cathode sheet is infiltrated in an electrolyte under a dry condition, and is electrified by an external circuit to form a SEI film on the surface of the cathode sheet, and after cleaning and drying, the cathode sheet and other components are assembled into a battery, thereby avoiding SEI generation during first-time formation and increasing first-time efficiency; however, this solution involves rigorous technological conditions and a tedious process, which causes great cost waste, and moreover, the cathode sheet requires multiple times of cleaning and drying after the film is formed, which has a great influence on performance of an electrode sheet in various aspects, especially a binding effect of the electrode sheet, and therefore cannot ensure safety of the lithium ion battery system, or (2) provide a “lithium source” to compensate lithium ions lost by the lithium ion battery in the first-time charge/discharge process, so as to reduce inreversible capacity, for example, US FMC company achieves a purpose of reducing inreversible capacity and increasing energy density, by providing lithium metal powder that exists stably in air-stabilized lithium Metal Powder (SLMP) and introducing it into the cathode material in a slurry mixing or rolling manner, that is, compensating lithium lost for forming the SEI film in the first-time charge-discharge process of the lithium ion battery by using the additionally introduced lithium source; however, in this solution, coating of the lithium metal is mainly lithium carbonate and a small amount of lithium oxide or lithium hydroxide and hydrocarbon, and lithium carbonate remained after the lithium source participates in reaction increases internal resistance of the system, and although one part of the lithium carbonate may be dissolved by very little hydrogen fluoride in the electrolyte, the performance of the lithium ion battery may still be affected.